From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9EA7C282CE for ; Wed, 22 May 2019 23:46:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6BED12173C for ; Wed, 22 May 2019 23:46:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727305AbfEVXqj (ORCPT ); Wed, 22 May 2019 19:46:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38822 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726218AbfEVXqi (ORCPT ); Wed, 22 May 2019 19:46:38 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5F88630832E6; Wed, 22 May 2019 23:46:38 +0000 (UTC) Received: from treble (ovpn-120-127.rdu2.redhat.com [10.10.120.127]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ECC1660857; Wed, 22 May 2019 23:46:36 +0000 (UTC) Date: Wed, 22 May 2019 18:46:35 -0500 From: Josh Poimboeuf To: Alexei Starovoitov Cc: Peter Zijlstra , Kairui Song , Song Liu , lkml , Kernel Team , Alexei Starovoitov , Daniel Borkmann , "bpf@vger.kernel.org" Subject: Re: Getting empty callchain from perf_callchain_kernel() Message-ID: <20190522234635.a47bettklcf5gt7c@treble> References: <3CD3EE63-0CD2-404A-A403-E11DCF2DF8D9@fb.com> <20190517074600.GJ2623@hirez.programming.kicks-ass.net> <20190517081057.GQ2650@hirez.programming.kicks-ass.net> <20190517091044.GM2606@hirez.programming.kicks-ass.net> <20190522140233.GC16275@worktop.programming.kicks-ass.net> <20190522174517.pbdopvookggen3d7@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190522174517.pbdopvookggen3d7@treble> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Wed, 22 May 2019 23:46:38 +0000 (UTC) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, May 22, 2019 at 12:45:17PM -0500, Josh Poimboeuf wrote: > On Wed, May 22, 2019 at 02:49:07PM +0000, Alexei Starovoitov wrote: > > The one that is broken is prog_tests/stacktrace_map.c > > There we attach bpf to standard tracepoint where > > kernel suppose to collect pt_regs before calling into bpf. > > And that's what bpf_get_stackid_tp() is doing. > > It passes pt_regs (that was collected before any bpf) > > into bpf_get_stackid() which calls get_perf_callchain(). > > Same thing with kprobes, uprobes. > > Is it trying to unwind through ___bpf_prog_run()? > > If so, that would at least explain why ORC isn't working. Objtool > currently ignores that function because it can't follow the jump table. Here's a tentative fix (for ORC, at least). I'll need to make sure this doesn't break anything else. diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 242a643af82f..1d9a7cc4b836 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1562,7 +1562,6 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) BUG_ON(1); return 0; } -STACK_FRAME_NON_STANDARD(___bpf_prog_run); /* jump table */ #define PROG_NAME(stack_size) __bpf_prog_run##stack_size #define DEFINE_BPF_PROG_RUN(stack_size) \ diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 172f99195726..2567027fce95 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1033,13 +1033,6 @@ static struct rela *find_switch_table(struct objtool_file *file, if (text_rela->type == R_X86_64_PC32) table_offset += 4; - /* - * Make sure the .rodata address isn't associated with a - * symbol. gcc jump tables are anonymous data. - */ - if (find_symbol_containing(rodata_sec, table_offset)) - continue; - rodata_rela = find_rela_by_dest(rodata_sec, table_offset); if (rodata_rela) { /*